Largest Map Ever Made Covers 1.2 Million Galaxies

Scientists have just created the largest map ever made: a three-dimensional model of 1.2 million galaxies, which measures the presence of dark energy in the universe with unprecedented accuracy.

"We have spent five years collecting measurements of 1.2 million galaxies over one quarter of the sky to map out the structure of the Universe over a volume of 650 cubic billion light years," team co-leader Jeremy Tinker of New York University said in a statement. "This map has allowed us to make the best measurements yet of the effects of dark energy in the expansion of the Universe. We are making our results and map available to the world."

The map, made using data from the Sloan Digital Sky Survey and its Baryon Oscillation Spectroscopic Survey, reveals highly clustered galaxies that form superclusters and voids, which are thought to compose the universe in a giant spider-web of galaxies. The below image is described as "one slice" of the groundbreaking map, and represents a section of the universe that's 6 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick, or approximately 1/20th of the night sky. Each dot represents a single galaxy, and maps its position 6 billion years ago. This image alone contains 48,741 galaxies, which represents only 3% of the full map.

But this model not only serves to map the position of galaxies in our universe, it also measures the elusive relationship between dark matter and dark energy, which in turn impacts the expansion rate of our Universe. It essentially amounts to a tug-of-war between dark energy and dark matter, in which dark matter's gravity pushes galaxies toward each other and dark energy pulls them apart.

"We've made the largest map for studying the 95% of the universe that is dark," said BOSS principal investigator David Schlegel. "In this map, we can see galaxies being gravitationally pulled towards other galaxies by dark matter. And on much larger scales, we see the effect of dark energy ripping the universe apart."

And once scientists can determine the expansion rate of the universe, they can glean the respective amounts of matter and dark energy that currently compose the Universe, which tells us more about our cosmic history than ever before.

"Measuring the acoustic scale across cosmic history gives a direct ruler with which to measure the Universe's expansion rate," said Shirley Ho of Carnegie Mellon University. "With BOSS, we have traced the BAO's subtle imprint on the distribution of galaxies spanning a range of time from 2 to 7 billion years ago."